http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53533
--- Comment #11 from Matt Hargett <matt at use dot net> 2012-06-12 18:25:25 UTC --- Richard, Thanks for the quick analysis! Sounds like a perfect storm of sorts :/ re: cprop failure: this may be indicated by another major regression in their suite for the "simple constant folding" tests. in GCC 4.1-4.6, those tests are all 0.0s but in 4.7 take tens of seconds. Let me know if you want me to file a separate bug/reduced test case for that, and then have that new bug depend on this one. Otherwise, I'll wait until this one sees some resolution and then retest. re: multiple passes: if you think that feature has enough merit to be revisited now, I can look into re-proposing Maxim's patches from October/November 2011 that integrated your feedback at the time. re: -march workaround: our deployment platform's minimum arch is nocona, and enabling -march=nocona doesn't workaround the issue. For grins, I tried -march=amdfam10 (another deployment target, but would require a separate distributable binary), but that also didn't work around the issue. I see a small improvement when using -fno-tree-vectorize, but not nearly as dramatic as yours. For the int32_t for and while loop unrolling, the times go from ~107s and ~105s to ~96s and ~95s, respectively. The do and goto loop unrolling times get slightly worse (~2%), but it might be noise. Let me know if there's any additional testing/footwork you'd like me to do. Again, thanks for the quick turnaround on such a deep analysis!
